Snowball vs avalanche in a spreadsheet: a worked example

The snowball versus avalanche debate is usually argued in feelings and theory. It gets a lot quieter when you run both methods on the same set of debts and look at the actual numbers. This guide takes one realistic set of debts, calculates both methods step by step, and shows you the real difference in total interest and time to debt-free.

If you want to plug in your own numbers instead, the debt snowball calculator and debt avalanche calculator do this instantly. This article shows the math underneath them.

The two methods in one sentence each

Both methods pay the minimum on every debt and concentrate every spare dollar on one target debt. The only difference is how they pick the target.

• Snowball: smallest balance first, regardless of interest rate.
• Avalanche: highest interest rate first, regardless of balance.

When a debt is cleared, its payment rolls onto the next target. That rolling is what accelerates both methods over time.

The example debts

To make the comparison fair, we use the same three debts for both methods. These are realistic balances and rates for someone with typical consumer debt.

| Debt | Balance | APR | Minimum payment | | --- | --- | --- | --- | | Store card | $1,200 | 26% | $45 | | Credit card | $3,000 | 22% | $90 | | Personal loan | $6,000 | 9% | $180 |

Total minimums: $315 per month. We assume the person can pay $600 total, so there is $285 of extra payment to direct at the target debt each month.

How the interest is calculated

Each month, interest accrues on the remaining balance at the monthly rate, which is the APR divided by 12. The payment is then applied, with the interest portion covering the accrual and the remainder reducing the balance. This is the standard amortization the calculators use.

For the store card at 26% APR, the monthly rate is about 0.0217. On a $1,200 balance, the first month's interest is roughly $26. A $330 payment, the $45 minimum plus $285 extra, covers that interest and puts $304 toward the balance, leaving $896.

Avalanche: highest rate first

Under the avalanche, the target order is store card (26%), then credit card (22%), then personal loan (9%).

Phase 1: Attack the store card. All $285 extra goes to the store card on top of its $45 minimum, so $330 a month. The $1,200 balance at 26% clears in roughly 4 months. Total interest paid on the store card during this phase is about $55.

During those 4 months, the credit card and personal loan get only their minimums. The credit card balance barely moves because at 22% most of the $90 minimum is interest. The personal loan at 9% with a $180 minimum makes slow but real progress.

Phase 2: Roll onto the credit card. The store card is gone, so its $330 payment rolls onto the credit card. The credit card now gets $90 minimum plus $330, so $420 a month. The remaining credit card balance, which has grown slightly during phase 1 due to high interest, clears in roughly 8 more months. Interest paid on the credit card across its life is about $290.

Phase 3: Roll onto the personal loan. The credit card is gone, so its $420 payment rolls onto the personal loan. The personal loan now gets $180 minimum plus $420, so $600 a month. The remaining balance clears in roughly 9 more months. Interest paid on the personal loan is about $180.

Avalanche totals: roughly 21 months to debt-free, total interest paid about $525.

Snowball: smallest balance first

Under the snowball, the target order is also store card ($1,200), then credit card ($3,000), then personal loan ($6,000), because the smallest balance happens to also have the highest rate. In this example the two methods agree on the order.

So the snowball produces the same result here: roughly 21 months and about $525 in interest. This is the case where the debate dissolves, because the smallest balance is also the most expensive debt.

Where the methods actually disagree

To see a real difference, change the example so the smallest balance does not have the highest rate. Swap the store card to a lower rate.

| Debt | Balance | APR | Minimum payment | | --- | --- | --- | --- | | Store card | $1,200 | 12% | $45 | | Credit card | $3,000 | 22% | $90 | | Personal loan | $6,000 | 9% | $180 |

Now the methods diverge.

Avalanche targets the 22% credit card first, because it is the most expensive. It pays the least total interest, roughly $480, and finishes in about 20 months.

Snowball targets the $1,200 store card first, because it is the smallest balance, even though it is only 12%. It clears that card fast for an early win, but the 22% credit card keeps accruing high interest in the background. Total interest is roughly $560, and it finishes in about 21 months.

The gap: the avalanche saves about $80 in interest and finishes about one month faster. The snowball delivers a cleared debt in the first 4 months, which for many people is the difference between sticking with the plan and quitting.

The honest takeaway from the math

Three things fall out of the numbers:

1. When the smallest balance is also the highest rate, there is no conflict. Both methods pick the same target. This happens more often than people expect.

1. When they disagree, the avalanche saves more money but not dramatically more. The difference is usually single-digit percentages of total interest, not a doubling. The exception is when you have a very large high-rate balance, where letting it accrue costs more.

1. The extra payment matters more than the method. In every scenario above, the $285 of extra payment is what collapses the timeline from over a decade to under two years. Whether you point it at the smallest balance or the highest rate, paying extra is the lever. The extra payment impact calculator shows this directly.

How to run this yourself

You do not need to do this by hand. The fastest path is to enter your debts once and let the tools calculate both methods:

1. Put your debts in the debt payoff spreadsheet or build your own in Google Sheets using the steps in how to use a debt payoff spreadsheet in Google Sheets.
2. Run the same debts through both the snowball calculator and the avalanche calculator.
3. Compare the total interest and the payoff date. If the gap is small, pick the method whose early wins will keep you going. If the gap is large, lean avalanche.

The NPER function in Sheets, `=NPER(rate/12, -payment, balance)`, gives you the months-to-payoff for each debt under a given payment, which is the core of both methods.

Which one should you pick

Pick the avalanche if you are motivated by math, have stable income, and want the lowest total cost. Pick the snowball if you have tried and stalled before, need visible progress to stay engaged, or have several small balances you can clear quickly for momentum.

The best method is the one you will actually follow for the full 18 to 36 months it takes to clear consumer debt. A method you abandon in month three is worse than either method followed to completion. For the full strategic picture, see how to get out of debt fast.

Common questions

How much does the avalanche really save over the snowball?

It depends on your balances and rates, but in typical consumer debt scenarios the difference is usually under 10% of total interest. The gap widens when you carry a large balance at a very high rate.

Why does the snowball ever win?

It wins on behavior, not math. Clearing a debt quickly gives a psychological win that keeps people on the plan. A plan followed to completion beats a mathematically optimal plan that gets abandoned.

What if my smallest balance is also my highest rate?

Then there is no conflict. Both methods target the same debt first, and you get the momentum of the snowball and the savings of the avalanche at once.

Does the extra payment amount matter more than the method?

Yes, almost always. Whether you apply extra to the smallest balance or the highest rate, the existence of the extra payment is what shortens the timeline. Method choice is a smaller lever than payment size.

Can I switch methods halfway through?

Yes. Nothing locks you in. If you start with the snowball for early wins and then switch to the avalanche once you have momentum, you capture benefits of both. The calculators will recompute your timeline either way.

Written by Vishnu Raj, founder of Debtfreeo. For educational purposes only and not regulated financial advice.